全文获取类型
收费全文 | 13034篇 |
免费 | 2356篇 |
国内免费 | 2041篇 |
专业分类
化学 | 9839篇 |
晶体学 | 254篇 |
力学 | 778篇 |
综合类 | 148篇 |
数学 | 1313篇 |
物理学 | 5099篇 |
出版年
2024年 | 23篇 |
2023年 | 278篇 |
2022年 | 401篇 |
2021年 | 493篇 |
2020年 | 589篇 |
2019年 | 593篇 |
2018年 | 540篇 |
2017年 | 506篇 |
2016年 | 707篇 |
2015年 | 731篇 |
2014年 | 870篇 |
2013年 | 1095篇 |
2012年 | 1360篇 |
2011年 | 1407篇 |
2010年 | 991篇 |
2009年 | 958篇 |
2008年 | 947篇 |
2007年 | 855篇 |
2006年 | 788篇 |
2005年 | 653篇 |
2004年 | 464篇 |
2003年 | 319篇 |
2002年 | 344篇 |
2001年 | 287篇 |
2000年 | 234篇 |
1999年 | 183篇 |
1998年 | 164篇 |
1997年 | 120篇 |
1996年 | 88篇 |
1995年 | 81篇 |
1994年 | 65篇 |
1993年 | 61篇 |
1992年 | 55篇 |
1991年 | 50篇 |
1990年 | 38篇 |
1989年 | 16篇 |
1988年 | 13篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1971年 | 2篇 |
1959年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
By using the quasi-Lyapunov function, some sufficient conditions of global exponential stability for impulsive systems are established, which is the basis for the following discussion. Then, by employing Riccati inequality and Hamilton-Jacobi inequality approach, some sufficient conditions of robust exponential stability for uncertain linear/nonlinear impulsive systems are derived, respectively. Finally, some examples are given to illustrate the applications of the theory. 相似文献
23.
24.
25.
We investigate the origin of ultraviolet (UV) emission from Mg0.12 Zn0.88 O alloy thin films with a wurtzite structure fabricated on c-plane Al2O3 substrates by plasma assisted molecular beam epitaxy. At room temperature, the absorption edge and UV emission band of the Mg0.12Zn0.88O film shift to high-energy side compared with ZnO films. Temperature dependence of the photoluminescence spectra shows that the UV emission is composed of free exciton and neutral donor bound exciton emissions. Two-step dissociation processes of the UV emission are observed with the increasing temperature. The thermal quenching mechanism is attributed to the dissociation of the free exciton from the neutral donor bound exciton in the low temperature region and the dissociation of free electron and hole from the free exciton in the high temperature region. 相似文献
26.
27.
具P-Laplacian算子型周期边值问题解的存在性 总被引:8,自引:0,他引:8
本文利用拓扑度理论和一些分析技巧讨论了具p—Laplacian算子型周期边值问题(φp(χ’))’+d/dt gradF(χ)+gradG(χ)=e(t),χ(0)=χ(T),χ’(0)=χ’(T)解的存在性,在对阻尼项d/dtgradF(χ)没有任何限制的前提下,给出了解存在的充分条件. 相似文献
28.
Wang Qing-Lun Zhao Bin Liao Dai-Zheng Yan Shi-Ping Cheng Peng Jiang Zong-Hui 《Transition Metal Chemistry》2003,28(3):326-330
The copper(II) complex Na2[Cu(pba)] · 6H2O has been synthesized and its structure determined. It consists of a novel two-dimensional network of [Cu(pba)]2– anions connected to each other through the sodium ion as a bridge. Spectroscopic and magnetic properties have been measured and a spin distribution calculation has been carried out with the GAUSSIAN-94. Theoretical calculations indicate the rather larger spin density on nitrogen atoms should be responsible for the satellite lines appearing beside the main hyperfine coupling signs of copper(II). The antiferromagnetic interaction may be due to the intermolecular interaction and/or different copper(II) ions through the Na+ bridge in the same layer. 相似文献
29.
30.
Shen-shui Lü 《高分子科学》2006,(5):441-447
Two kinds of water-soluble metallophthalocyanines, binuclear cobalt phthalocyanine (Co2Pc2) and binuclear ferric phthalocyanine (Fe2Pc2), were synthesized through phenylanhydride-urea route and characterized by elemental analysis and FT-IR spectra. Binuclear metallophthalocyanine derivatives (Mt2Pc2) were immobilized on silk fibers and modified viscose fibers to construct bioactive fibers of mimic enzyme. Mt2Pc2 was used as the active center of bioactive fibers, viscose and silk fibers as the microenvironments. The catalytic oxidation ability of bioactive fibers on the malodors of methanthiol and hydrogen sulfide was investigated at room temperature. The experimental results indicated that the catalytic activity of such bioactive fibers was closely correlative to the types ofbioactive fibers and substrates. 相似文献